Leung P C, Minegishi T, Ma F, Zhou F Z, Ho-Yuen B
Endocrinology. 1986 Jul;119(1):12-8. doi: 10.1210/endo-119-1-12.
The present study examines the possibility that, in the rat corpus luteum, an initial action of prostaglandin F2 alpha (PGF2 alpha) is to induce a ligand-stimulated breakdown of membrane inositol phospholipids. Luteal cells in primary culture were prepared from immature rats after PMSG and human CG priming. In 32P-prelabeled cells, PGF2 alpha caused a rapid decrease in the level of radiolabel found in phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate, as early as 20 sec after addition of the hormones. At 1 and 2.5 min, the effect of 10(-6) M PGF2 alpha on phosphatidylinositol 4,5-bisphosphate was significantly greater than that caused by 10(-6) M LHRH in identical cell cultures. By contrast, the levels of the 32P-prelabeled phosphatidylinositol and phosphatidic acid were increased at 5 min by PGF2 alpha or LHRH. Concomitant with the alterations in cellular levels of 32P-prelabeled phospholipids, PGF2 alpha markedly enhanced the accumulation of 3H-labeled inositol phosphates, i.e. inositol 1-phosphate, inositol diphosphate, and inositol triphosphate, during a 5-min incubation. A significant increase of radiolabeled inositol diphosphate was seen as early as 1 min after the addition of either PGF2 alpha or LHRH; PGF2 alpha was more effective than LHRH in this regard. The stimulatory effect of LHRH on inositol phosphate accumulation could be blocked completely by the concomitant presence of a potent LHRH antagonist, and at the concentration used (10(-6) M) the effects of PGF2 alpha and LHRH were not additive. Interestingly, the addition of an exogenous phospholipase C also caused a similar enhancement of inositol phosphate accumulation in identical cell cultures. For the first time, these data suggest that, at the level of the corpus luteum, hydrolysis of phosphoinositides may immediately follow PGF2 alpha (and to a lesser extent LHRH) receptor binding, and this in turn may lead to the generation of 1,2-diacylglycerol and inositol phosphates, resynthesis of phosphatidic acid and phosphatidylinositol, and mobilization of Ca2+.
本研究探讨了在大鼠黄体中，前列腺素F2α（PGF2α）的初始作用是否是诱导膜肌醇磷脂的配体刺激分解。在给予孕马血清促性腺激素（PMSG）和人绒毛膜促性腺激素（hCG）预处理后，从未成熟大鼠制备原代培养的黄体细胞。在32P预标记的细胞中，早在添加激素后20秒，PGF2α就导致磷脂酰肌醇4-磷酸和磷脂酰肌醇4,5-二磷酸中放射性标记水平迅速下降。在1分钟和2.5分钟时，10^(-6)M PGF2α对磷脂酰肌醇4,5-二磷酸的作用在相同细胞培养物中明显大于10^(-6)M促黄体生成素释放激素（LHRH）所引起的作用。相比之下，PGF2α或LHRH在5分钟时使32P预标记的磷脂酰肌醇和磷脂酸水平升高。伴随着32P预标记磷脂细胞水平的变化，在5分钟孵育期间，PGF2α显著增强了3H标记的肌醇磷酸的积累，即肌醇1-磷酸、肌醇二磷酸和肌醇三磷酸。早在添加PGF2α或LHRH后1分钟就可见放射性标记的肌醇二磷酸显著增加；在这方面PGF2α比LHRH更有效。LHRH对肌醇磷酸积累的刺激作用可被强效LHRH拮抗剂的同时存在完全阻断，并且在所用浓度（10^(-6)M）下，PGF2α和LHRH的作用不是相加的。有趣的是，添加外源性磷脂酶C在相同细胞培养物中也引起了类似的肌醇磷酸积累增强。这些数据首次表明，在黄体水平，磷酸肌醇的水解可能在PGF2α（以及在较小程度上LHRH）受体结合后立即发生，这反过来可能导致1,2-二酰基甘油和肌醇磷酸的生成、磷脂酸和磷脂酰肌醇的再合成以及Ca2+的动员。
